THE COMPANY MAINTENANCE PERSONNEL WERE AWARE OF A SHIMMY PROBLEM BUT THEY THOUGHT IS WAS ONLY WORN BUSHINGS. THE MAINTENANCE PEOPLE STATED THEY INSPECTED THE PART BUT FOUND NO PROBLEM. THE PILOT-IN-COMMAND ALSO STATED HE FOUND NO PROBLEM UPON VISUALLY INSPECTING THE ASSEMBLY JUST PRIOR TO THE INCIDENT. THE RECORDS DO NOT INDICATE A LANDING GEAR CHANGE, HOWEVER, THE WRONG PART WAS INSTALLED AS OUTLINED IN THE PARTS MANUAL. FURTHERMORE, AN UNCERTIFICATED ASSISTANT TO THE DIRECTOR OF MAINTENANCE RELEASED THE AIRPLANE WITHOUT HAVING A QUALIFIED MECHANIC INSPECT THE GEAR. THE PILOT-IN-COMMAND ACCEPTED THE AIRPLANE WITH A KNOWN DEFICIENCY AND DID NOT ENTER THE DISCREPANCY UNTIL AFTER THE INCIDENT. THE LEFT MAIN LNDG GEAR COLLAPSED DURING LANDING. THE GEAR HAD 'WOBBLED' DURING TAXI AT ANCHORAGE. THE PLT AND A BAGGAGE HANDLER HAD INSPECTED THE GEAR AND FOUND NOTHING OUT OF ORDER. THE PLT TELEPHONED CO MAINTENANCE AND THE CO GEN MGR SAID THE CO WAS AWARE OF THE SHIMMY PROBLEM AND TO TAKE THE FLT.